1. Field of the Invention
The present invention relates to improved dryer added fabric conditioning articles and methods for providing softening and static control properties to fabric in an automatic clothes dryer. The invention further relates to improved fabric conditioning compositions and the process of making said fabric conditioning compositions. More particularly, these fabric conditioning compositions comprise compounds having quaternary ammonium functionality(s) and ester linkages therein. The fabric conditioning compositions further contain mixtures of glycerin, mono-, di- and triglycerides. The fabric conditioning compositions are preferably releasably attached to a flexible substrate, e.g., a dryer sheet, but may also be in liquid form, particulate form, or compounded with other materials in solid form, e.g., tablets, pellets agglomerates, etc.
2. Description of the Related Art
The use of fabric conditioning compositions to treat fabric during the laundering process to soften the fabric, give the fabric greater bulk, make the fabric easier to iron, decrease the fabric drying time and reduce the static charge on the fabric is well known in the art. Fabric softness or conditioning is usually understood to be that quality of the treated fabric whereby its handle or texture is smooth, pliable and fluffy to the touch. Fabric conditioning also connotes the absence of static “cling” or static electricity in the fabrics, and in general, fabric conditioning compositions or fabric softeners provide both softening and antistatic benefits when applied to fabric.
Fabric conditioning compositions may be utilized in the washing cycle and/or the drying cycle of the laundering process. Fabric conditioning compositions, which are utilized during the drying cycle in automatic tumble dryers, are typically attached to a flexible substrate, e.g., a dryer sheet. The fabric conditioning composition is coated onto the dryer sheet and the resulting fabric softener sheet is commingled with moist fabrics in an automatic laundry dryer. The heating and tumbling action of the dryer aids in the transfer of the fabric conditioning composition from the dryer sheet to the fabric surface. Several known advantages of dryer-added fabric conditioning compositions, over wash cycle added fabric conditioning compositions, include a more convenient time of addition in the laundering process, avoidance of fabric conditioning composition/washing detergent composition incompatibility and an optimized, pre-measured amount of the fabric conditioning composition.
Fabric conditioning compositions applied during the drying cycle in automatic clothes dryers have a very different focus as compared to rinse added fabric conditioning compositions. Unfortunately, by statistical testing it is difficult, if not impossible, to quantitate differences in the softening performance delivered by different brands of commercially available fabric softener sheets because of the non-uniform mass transfer of active ingredients from the flexible substrate to the fabric surface. The softening performance delivered by commercial fabric softener sheets is often a subjective quality which varies greatly with different consumers.
Fabric softener sheets function primarily as a means to reduce static and as a carrier of perfume and other optional ingredients. In order to function properly, the fabric conditioning compositions present on the sheets must have a proper melt range, a suitable substrate release profile, and uniform damp fabric spreadability without spotting or staining the fabric. Some fabric softening compositions adhere to the dryer sheet too strongly, causing incomplete transfer of the softener to the fabric, less than complete transfer requires the use of excess softening material on the dryer sheet to assure sufficient static reduction, perfume delivery and conditioning effects. The use of high levels of fabric conditioning composition on the dryer sheets is inefficient and may in turn lead to deposition of concentrated patches of fabric conditioning composition on the fabric causing an undesirable stain.
Typically, fabric conditioning compositions for use in dryer sheet applications are heated from about 160° F. to about 180° F. and transferred onto a fabric substrate or web via a high speed coating or spraying process. After the web is contacted with the molten active components, it is cooled to a temperature where the softening coating is no longer tacky. The web is then perforated, spooled, cut and packaged. The melting point and viscosity characteristics of the fabric conditioning composition are critical factors which affect dryer sheet production rate and consumer acceptance; high viscosity materials can put a drag on the web and cause it to break, forcing slower web speeds. From a consumer point-of-view, the finished product must be tack-free and must not bleed when packaged within a box, even during extended storage at elevated warehouse or trucking temperatures.
Thus, a continuing need is recognized in the art to increase the evenness and the completeness of transfer of the fabric conditioning composition from the dryer sheet to the fabric. Further needs are also recognized in the art for fabric conditioning compositions with proper melt ranges, viscosities, release characteristics from the substrate, and spreading properties on the damp fabric so that the fabric conditioning compositions distribute relatively uniformly, without spotting or staining said fabric.
Various approaches have been taken in the prior art to overcome the aforementioned limitations and problems of fabric softening compositions coated on dryer sheets. In general, the term “esterquat” is defined as a compound which posses one or more quaternary nitrogens and one or more ester functionalities.
Fatty alkyl cationic antistatic softening compositions for use in automatic dryers have been the subject of many patents. For example, see U.S. Pat. No. 3,634,947, Furgal, issued Jan. 18, 1972, and U.S. Pat. No. 3,676,199, Hewitt et al., issued Jul. 11, 1972.
Three major fabric softener compositions are currently used in commercial dryer sheet applications. The first fabric softener which is employed on a commercial scale in laundry detergents, softening rinses and dryer sheets is N-dihydrogenatedtallow-N,N-dimethylammonium sulfate (DHTDMAS). The use of this material in a dryer sheet application is the subject of U.S. Pat. No. 3,944,694, McQueary, issued Mar. 16, 1976. The second composition involves the use of dihydrotallow dimethylammonium methosulfate in combination with a nonionic component such as polyethylene glycol esters or stearic acid ethoxylates (2-4 moles), in a 70:30 ratio. The use of this material in a dryer sheet application is the subject of U.S. Pat. No. 4,159,356, Jablonski, issued Jun. 26, 1979. The third composition involves the use of hard tallow imidazolinium quaternary compounds, in combination with a nonionic component such as polyethylene glycol esters or stearic acid ethoxylates (2-4 moles), in varying ratios. This material is sold under the name Accosoft® PX57-S or 870, manufactured by Stepan Company, Northfield, Ill.
Other components have been patented for use in dryer sheets, such as diamidoamine ethoxylates based on hard tallow, in U.S. Pat. No. 4,906,410, Lacke et al., issued Mar. 6, 1990; sorbitan esters with hard fatty acids, in U.S. Pat. No. 4,096,071, Murphy, issued Jun. 20, 1978; salts formed from mono and di-alkyl amines and anionic surfactants, in U.S. Pat. No. 4,824,582, Nayar, issued Apr. 25, 1989, U.S. Pat. No. 4,786,422, Kern, issued Nov. 22, 1988 and U.S. Pat. No. 4,882,076, Kern, issued Nov. 21, 1989; DHTDMAS with polydiorganosilanes, in U.S. Pat. No. 4,767,548, Kasprzak, et al., issued Aug. 30, 1988; N-alkyl-N,N-dimethyl amine oxides in combination with DHTDMAS, in U.S. Pat. No. 5,080,810, Smith, et al., issued Jan. 14, 1992; and ethoxylated piperazine ester quats, in U.S. Pat. No. 5,128,053, Gummo, et al., issued Jul. 7, 1992. The use of minor amounts of fatty esters of sorbitan polyols in conventional fatty alkyl substituted quaternary ammonium salt softening compositions has also been shown to provide improved release of the softening compositions from the dryer sheet.
In the last 5 years, soil release agents have been incorporated into fabric softening composition which are deposited on dryer sheets to create a multi-functional, fabric enhancing product, as described in U.S. Pat. No. 4,749, 596, Evans, et al., issued Jun. 7, 1988 and U.S. Pat. No. 4,764,289, Trinh, issued Aug. 16, 1988. The latest technology focus has been the development of fragrance persistent formulations using cyclodextrins to trap volatile components, as disclosed in U.S. Pat. No. 5,102,564, Gardlik, et al., issued Apr. 7, 1992 and U.S. Pat. No. 5,234,610, Gradlik, et al., issued Aug. 10, 1993.
Other related developments revolve around packaging, such as the folded single napkin dryer sheet product disclosed in U.S. Pat. No. 5,305,881, Caldwell, et al., issued Apr. 26, 1994.
Recent esterquat developments rely on a low melting esterquat combined with a DHTDMAS type quaternary ammonium compound in a ratio of about 1:10 to about 2:1. This material is further combined with an acid or ester, preferably citric acid.
The usual raw materials for the production of esterquats have been methyl esters and/or fatty acids. These fatty sources arm condensed with triethanolamine (TEA), methyldiethanolamine (MDEA), or alkoxylated/propoxylated derivatives of DEA and MDEA, to produce an intermediate esteramine product Typically when TEA is utilized, the ratio of fatty acid or methyl ester to TEA is adjusted to favor the formation of a di-ester condensation product which is formed along with the mono- and trimesters in a wt. % ratio approximating 20/60/20 mono:di:tri The mixed intermediate esteramine product is subsequently subjected to an alkylation reaction with dimethyl sulfate (DMS) to form a mixture of esterquats. A commercial example of these types is Stepantex® VA-90 (Stepan Company, Northfield Ill.).
Typically, the esterquat products of the alkylation reaction described above must have solvent added to them in order to keep the viscosity of the products in a manageable range which is typical for commercial rinse-added softener bases. Thus, nearly all esterquat products for rinse added softener applications contain at least 10% of an alcohol whose primary purpose is to lower the pour point and viscosity, and facilitate formulation. Alcohols such as isopropanol, propylene glycol, and dipropylene glycol have been used at 10-20 weight % based on the total weight of the composition. For virtually all dryer sheet manufacturers, this product is unsuitable due to the high level of VOC's (volatile organic compounds) which would be released during the heating and coating processes, and the attendant flammability issues.
A patent application, EP 580527 A1, discloses cationic surfactant compositions comprising, in quaternary ammonium salt form, the condensation product of a triglyceride and a tertiary amine, namely TEA (triethanolamine). The resulting compositions are useful as fabric softeners, hair conditioners, antistatic agents, lubricants, etc. This technology involves the reaction of whole triglycerides, optionally along with fatty acids, with TEA to generate interesterification products. The ratio of triglyceride to fatty acid to TEA allows control of the product mixture statistical distribution so that the di-ester of TEA predominates along with the mono-ester of glycerin. These are true statistical distributions, so that free glycerin, and mono-, di- and tri-glycerides are all formed, as are the mono- di- and tri-esters of TEA. The triglycerides and fatty acids may be animal or vegetable derived, and may be either saturated or unsaturated, or mixtures thereof.
These products are then quaternized with DMS in the presence of a low molecular weight alcoholic solvent, and may be formulated into concentrated rinse-addable products which contain esterquat in about 1-25% weight percent, based on the total weight of the formulation. The mono-, di- and tri-glycerides are known to be complementary active softening ingredients.
It has now been surprisingly discovered that new compositions based on homogeneous blends of mixed acyloxyalkyl quaternary ammonium compounds, in the presence of glycerin, and mono-, di- and triglycerides am fabric conditioning compositions that provide static control and softness to fabric in an automatic clothes dryer.
The invention therefore provides static control and softness to fabric treated with mixed acyloxyalkyl quaternary ammonium compounds, glycerin, and mono-, di-, and triglycerides. The invention further alleviates many of the aforementioned difficulties and limitations of fabric conditioning compositions currently used in current dryer sheet applications. The compositions of the present invention are substantially free of low-molecular weight glycol and alcoholic solvents and are particularly useful as fabric softening compositions in automatic dryer sheet applications.
This and other objects are obtained herein, as will become apparent from the following disclosure. The terms alkyl and alkenyl are defined as hydrocarbon radicals which are saturated and unsaturated, respectively.
It is therefore an object of the present invention to provide static control and softness to fabric treated with mixed acyloxyalkyl quaternary ammonium compounds, glycerin, mono-, di- and triglycerides. It is further and object of the present invention to alleviate many of the aforementioned difficulties and limitations of fabric conditioning compositions currently used in current dryer sheet applications. The compositions of the present invention are substantially free of low-molecular weight glycol and alcoholic solvents and are particularly useful as fabric softening compositions in automatic dryer sheet applications.
This and other objects are obtained herein, as will become apparent from the following disclosure. The terms alkyl and alkenyl are may defined as hydrocarbon radicals which are saturated and unsaturated, respectively.